JOPLIN, Mo. — When the warning — “Execute Condition Gray!” — blared through the halls of St. John’s Regional Medical Center, nurses began rolling patients’ beds into the hallways, as they had been trained to do time and again in this tornado-prone region.

But just as workers were completing the precautionary steps Sunday night, the entire nine-story building was pummeled by a tornado. Glass shards exploded from every window, doors blew open, and even patients’ IV-lines were ripped from their arms.

By the time the three-quarter-mile-wide tornado — among the deadliest in the nation’s history — moved on, the hospital was a scene of stunned chaos. Nearly every patient was splashed or covered with blood from all the glass, and people in the emergency room on the first floor were sucked out of windows into the parking lot. Even a backup generator failed, leaving ventilators and other medical equipment without power in dark rooms.

One panicked nurse, who had been in the intensive care unit, pleaded for help when machines stopped pumping air into the lungs of critically ill patients. “I’ve got patients dying up there!” Robert Kuhn, a hospital worker, recalled the nurse calling out. The doctors told him to go back and pump the air manually.

At least 116 people were killed and hundreds more injured, city officials said Monday, as hundreds of emergency workers searched for others beneath the rubble that blanketed this southwest Missouri city. Leaders said they expected the death count to continue to rise.

The tornado, which struck around dinner time, crushed nearly a third of the city. It pounded about 2,000 buildings, knocked out power and cellphone service for many, and damaged water treatment and sewage plants. The tangled remains of cars and trucks were overturned and thrown against buildings and trees. Some blocks were jagged mounds of debris, while others were stripped to utter emptiness: just foundations of homes and tree trunks — no leaves, no branches, no bark.

The tornado did catastrophic damage to a Wal-Mart, a high school and a nursing home apartment building, and ripped through the places that exist to respond to emergencies, like a fire station, where a brick wall was crumbled over a fire truck, and the hospital, whose sign was reported to have been spotted miles from Joplin.

It was the deadliest single tornado in more than half a century, and it adds to a season of particularly deadly tornadoes. Storms in the Midwest and South have killed hundreds of people in the last two months, and left millions of dollars of damage behind.

The latest tornado was part of a weather system in which cold and warm fronts crashed together throughout the middle of the country, creating conditions that can spawn “supercell” thunderstorms like the one here.

From a state trip to Europe, President Obama issued condolences, saying the families of Joplin were in his thoughts and prayers, and sent emergency management officials to Missouri to assist.

“At my direction, FEMA is working with the affected areas’ state and local officials to support response and recovery efforts, and the federal government stands ready to help our fellow Americans as needed,” a statement from the White House said.

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A storm bore down on devastated Joplin, Mo., on Monday. St. John's Regional Medical Center, which Sunday's tornado hit directly, is at left in the background.Credit
Julie Denesha/Getty Images

In Joplin, along with the hundreds of state and federal workers, ordinary people, exhausted and ragged from their own struggles overnight and armed with tools from their own garages, spent much of the day Monday searching for friends, relatives, even strangers. About 49,000 people live here, and few lives were untouched.

Cheyanna Padilla, 19, said she had lived through the storm by clinging to a urinal inside the Wal-Mart store. She prayed, she said, as the roof crumpled on top of her, then she climbed out wondering how many might be dead beneath her.

The search, which continued into Monday evening, was complicated by bouts of pounding rain, thunderstorms and bursts of hail, along with constant worries that another twister would sweep up what was left of the community.

Gov. Jay Nixon said rescuers had found at least five families still alive under the rubble.

But many had far grimmer tales. Mark Stepp, whose house was destroyed, spent the day digging out homes. Beneath one, he said, he found the body of a young girl — a discovery that left him vomiting at the street’s edge. “I found a little girl,” he said, pacing and frantically puffing on a cigarette. “I’m so freaked out.”

Of the 183 patients at St. John’s on Sunday night, five died as a result of the tornado, a hospital official said. All had been in critical condition before the storm, he said.

The rest — some of them injured in the storm, adding to the problems that put them in the hospital in the first place — were sent to other hospitals in three states. In the confusion of the day, some patients’ family members found themselves driving from hospital to hospital, looking and worrying.

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Emergency workers waited for a medical team after finding a body in a car in Joplin, Mo., on Monday.Credit
Charlie Riedel/Associated Press

“Do they have a list? Do they have a list?” Kimberly Cain called out, as she and her son arrived at an emergency command post. She was searching for her husband, who had been on the fifth floor of St. John’s when she last heard from him. There were no lists, she was told, or at least none that anyone knew of. There had not been time.

A tornado warning was issued in Joplin a relatively lengthy 24 minutes before the tornado struck, officials say, though workers at St. John’s said the warning system in their building had given far less time. From the moment that alarm went off, though, they worked through the procedures designed to protect patients and themselves. But they were quickly overwhelmed by the force of the tornado.

“We practice and practice this stuff, but this hit us so hard and so fast it was just gut reaction,” said Gary Pulsipher, the president and chief executive of the hospital, which is a level-two trauma center.

Even as the nurses and doctors were finishing moving furniture, closing blinds and bringing patients into the hallways, the tornado struck. Tracy Merrill, a hospital worker, said he had dived onto an elderly cancer patient to protect her as glass flew through the hallway and walls began to cave in.

Tim Randolph, 48, was in the emergency room for treatment of a broken rib when the ceiling started shaking, the windows shattered, and the tornado raced inside. “It sucked the wind out of me,” said Mr. Randolph, who would later learn that he had three broken ribs, not just the one.

“The whole building was shaking,” said Misty Hicks, a nurse, who felt pressure in her ears, the roar of the tornado, and then saw a patient flipped over and pinned by the hospital bed against a wall. “That’s the scariest thing I’ve ever had to endure,” she said.

Video

TimesCast | Massive Twister In Missouri

Suddenly, the rooms went dark. Staff members and patients were scattered across the floor, and IV tubes, medicine and glass shards were everywhere. “Everyone was bloody,” Ms. Hicks said, remembering walking patient to patient with her flashlight.

Cellphones did not work, nor did land lines, and the hospital’s radios were down. People carried patients outside; those who could walk did, sometimes in bare feet over glass. Someone with a broken hip gave up his wheelchair to transport sicker patients.

Out in the parking lot, as night fell, hospital workers used any method they could to get patients care. Some worked despite bloody cuts and gashes of their own; others stepped away in shock. A city school bus and the beds of some pickup trucks were used to rush patients to other hospitals.

“It was mass chaos trying to get patients out,” said Sgt. Rodney Rodebush, a National Guard soldier who served in Iraq and Afghanistan and found himself outside St. John’s.

Sergeant Rodebush said he had carried about 25 patients out. He also found a dead woman dressed in her pajamas outside the hospital entrance.

On Monday morning, the hospital temporarily became a shelter again, this time for rescuers concerned that another tornado was approaching. In the middle of the lobby under an atrium, they found a few survivors: fish in an unbroken tank, swimming through the water.

Monica Davey contributed reporting from Chicago.

A version of this article appears in print on May 24, 2011, on page A1 of the New York edition with the headline: A Rush to Protect Patients, Then Bloody Chaos. Order Reprints|Today's Paper|Subscribe